Mayor de Blasio last week claimed “impressive gains” for the schools in his signature $383 million Renewal turnaround program. We wish it were true.

By the numbers, these schools did make some gains on state exams, relative to other city schools. But that’s largely, maybe exclusively, because the state Regents “dumbed down” the tests.

Simply put: If you make it easier to score as “proficient” (as the Regents have done), then schools where most kids weren’t testing as proficient will make bigger gains than schools where most kids were passing.

And even this mirage of a gain doesn’t make up for the ground the Renewal schools lost in the first two de Blasio school years.

Pretend the progress is real, and the math-proficiency gap between Renewals and the rest of the city still grew from 25.1 points in 2013 to 28.4 points in 2017. The English-proficiency gap grew from 20.2 points in 2013 to 24.7 points.

Plus, Team de Blasio has had to close or merge several of the original 94 persistently failing Renewal schools, thanks to plummeting enrollment or woes too serious for even this administration to tolerate: Only 78 will open this fall.

A Post series this spring shined a spotlight on the Renewal mess: On top of falling enrollment, they suffer from skyrocketing costs, unfit teachers and regular grade-fixing scams. A later Post investigation showed that at least 242 graduates at Renewal high schools earned their diplomas via an appeals process that allowed students to “pass” the Regents’ exams with normally too-low scores.

At least the mayor’s credit actions are more realistic than his happy talk: The city has announced that more Renewal schools soon will be slated for closing or merger — and several will get new principals this year.

The fact remains: His orders have left thousands of students wasting years failing to learn at schools he should have closed back in 2014. He kept them open in a bid to “prove” they could be turned around instead.

Every child stuck at these schools is a victim of his effort to experiment with their lives.